;o8 



NATURE 



[May 12, 1910 



In speaking of tar fuel, on p. 5, the authors say : — 



"The modern tendency, however, is to distil the tar 

 first, and recover its many valuable constituents such 

 as benzene, naphtha, carbolic acid, naphthalene, creo- 

 sote, and also the tar colours discovered by Perkin." 



This looseness of expression might lead some to be- 

 lieve that the coal-tar colours were a distillate from 

 tar. 



A few pages further on solid fuels are subdivided 

 into organic and inorganic, the latter consisting of 

 sulphur, silicon, phosphorus, and aluminium, the 

 latter being credited with giving a heat quite equal 

 to that produced in electric furnaces, a statement 

 which will be doubted -by the users of "Thermit." 



In the chapters devoted to the construction of the 

 modern form of bye-product recovery coke-oven, the 

 authors are at their best, and this portion is well 

 illustrated with many reproductions of photographs 

 from existing plants, as well as elaborate sections and 

 plans, yet the same* fault is to be found as in other 

 parts of the book, that is, the principles which govern 

 the various stages in the process of carbonisation, and 

 the chemical changes taking place during the opera- 

 tions, are ignored, whilst details of mechanical in- 

 terest only are elaborated. 



In the preface the reader is told that the book 

 embodies a series of lectures delivered at a technical 

 college to a class of men engaged on coke-ovens, and, 

 interesting as they must have been to the audience, it 

 cannot be too strongly impressed upon those delivering 

 lectures of this kind that, unless there is given a 

 foundation of scientific facts and theory upon which 

 the practical man can build and evolve original ideas, 

 the value of such lectures must be enormously les- 

 sened. 



Not only is the theory of carbonisation neglected, 

 but the coke produced during the process of gas 

 manufacture is hardly mentioned, although the gas 

 coke produced in the United Kingdom more than 

 doubles in quantity that made in bye-product recovery 

 plants, the beehive coke-oven, with its wicked waste 

 of tar and sulphate of ammonia, still being the most 

 favoured means of squandering our already depleted 

 coal-measures. 



At the present time there is a great opening for 

 an author who, with scientific knowledge of the sub- 

 ject, can gather together the work of Stein, Flack, 

 Richters, Muck, Parry, Thorner, Lunge, Knublauch, 

 and others on the carbonisation of coal, and weave 

 into tangible shape the lines upon which economy 

 of coal, abolition of smoke, increase of manurial 

 ammonium compounds, and enhanced values for our 

 tar products can be obtained. 



THE HUMAN CENTRAL NERVOUS SYSTEM. 

 Voordrachten over den Boiiw van het centrale 



Zenuwstelsel — een Voorbereiding tot de Kliniek der 



Zenuwziekten. Door Prof. J. W. Langelaan. Pp. 



vi+485, and 309 text-figures. (Amsterdam : A. 



Versluys, 1910.) 



THIS consists of the course of instruction on the 

 embryology and anatomy of the human nervous 

 system given in Leyden in the sessions 1907-8 and 

 NO. 2 1 15, VOL. 83] 



1908-9 put into the form of a book, which is illus- 

 trated with an excellent series of photographs of 

 sections and drawings by Heer G. Koster. It is 

 quite a revelation to find what soft effects of light 

 and shade the artist has obtained with pen and ink, 

 without sacrificing accuracy and clearness, in the 

 production of these admirable illustrations. 



The book is subdivided into four sections, dealing 

 respectively with (A) the development of the human 

 central nervous system (pp. 1-98) ; (B) the nature and 

 histogenesis of the nervous tissues (pp. 99-137); {Cy 

 the form of the various parts of the central nervous 

 system (pp. 138-286) ; and (D) the structure of the 

 central nervous system (pp. 287-485). 



The most distinctive section of the book is part A. 

 Part B contains a good and impartial summary of 

 the present state of our knowledge concerning the 

 mode of development and the nature of nerve-fibres 

 and cells, and supplies the reader with a good biblio- 

 graphy. Although parts C and D, on the whole, 

 are excellent accounts of the subjects of which they 

 treat, they present no special features which the 

 student cannot find elsewhere in text-books written 

 in languages more generally understood than Dutch 

 is. Moreover, the text of these sections is not so 

 " up-to-date," nor is the bibliography so satisfactory 

 as those of the early sections. 



Section A is a model of the manner in which 

 embryology should be taught to medical students. 



It begins with a clear account of the early stages 

 of development of the primate embryo, leading up to 

 the formation of the nervous system, and then de- 

 scribes the history of the further growth and differen- 

 tiation of the brain and spinal cord in human 

 embryos. Most books on embryology are rendered 

 confusing to the student by the introduction of de- 

 scriptions of what happens in the chick or the 

 developing rabbit, with tags of miscellaneous informa- 

 tion concerning the embryos of other vertebrates, and 

 the plea is urged in support bf such a mode of 

 procedure that it is the comparative method. But the 

 use of data culled from comparative anatomy in 

 works on human anatomy can be justified only when 

 they help to elucidate the latter or explain some 

 general principle which cannot be appreciated from 

 the mere study of one vertebrate ; unless the in- 

 formation directly serves one of these two purposes 

 it is w-orse than useless to insert it. One of the great 

 merits of Prof. Langelaan 's work is that it gives a 

 straightforward account of the human brain and its 

 development ; and no comparative data are inserted 

 in the embryological section except to explain stages 

 in human development which are not known from 

 direct observation of human material ; and then he is 

 careful to rely almost exclusively on information 

 obtained from the study of the mammals most nearly 

 related to man that supply the desired facts. 



A considerable part of the embryological section 

 of the work is based upon the author's own re- 

 searches, which are already familiar to readers of 

 Brain (1908) and the Anatomischer Anzeiger (1908);, 

 and this fact gives section A the freshness which 

 springs from first-hand knowledge, in contradistinc- 

 tion to the staleness of conventional errors which 



